<template>
    <div class="pagination">
        <!-- 上 -->
        <button :disabled="pageNo==1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
        <button v-if="startNumAndEndNum.start>1" @click="$emit('getPageNo',1)"  :class="{active:pageNo==1}">1</button>
        <button v-if="startNumAndEndNum.start>2">···</button>
        
        <!-- 中 -->
        <button v-for="(page,index) in startNumAndEndNum.end" v-show="page>=startNumAndEndNum.start" :key="index" @click="$emit('getPageNo',page)" :class="{active:pageNo==page}">{{page}}</button>
        
        <!-- 下 -->
        <button  v-if="startNumAndEndNum.end<totalPage-1">···</button>
        <button  v-if="startNumAndEndNum.end<totalPage" @click="$emit('getPageNo',totalPage)" :class="{active:pageNo==totalPage}">{{totalPage}}</button>
        <button :disabled="pageNo==totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>
        
        <button style="margin-left: 30px" >共 {{total}} 条</button>
    </div>
</template>

<script>
  export default {
    name: "Pagination",
    props:['pageNo','pageSize','total','continues'],
    computed:{
        //总共多少页
        totalPage(){
           return  Math.ceil(this.total/this.pageSize);
        },
        startNumAndEndNum(){
          let {continues,totalPage,pageNo}=this;
          // 定义2个变量存储起始和结束数字
          let start =0,end=0;
          // 不正常现象【总页数没有连续页数多】
          if(continues>totalPage){
            start=1;
            end=totalPage;
          }else{
            // 正常现象【总页数大于连续页数】
            start=pageNo-parseInt(continues/2);
            end=pageNo+parseInt(continues/2);
            // 把出现不正常的现象【start出现0|负数】纠正
            if(start < 1){
              start = 1;
              end = continues;
            }
            // 把出现不正常的现象【end大于总页码】纠正
            if(end > totalPage){
              start=totalPage-continues+1;
              end=totalPage;
            }
          }
          return {start,end};
        }
    }
  }
</script>

<style lang="less" scoped>
  .pagination {
    text-align: center;
    button {
      margin: 0 5px;
      background-color: #f4f4f5;
      color: #606266;
      outline: none;
      border-radius: 2px;
      padding: 0 4px;
      vertical-align: top;
      display: inline-block;
      font-size: 13px;
      min-width: 35.5px;
      height: 28px;
      line-height: 28px;
      cursor: pointer;
      box-sizing: border-box;
      text-align: center;
      border: 0;

      &[disabled] {
        color: #c0c4cc;
        cursor: not-allowed;
      }

      &.active {
        cursor: not-allowed;
        background-color: #409eff;
        color: #fff;
      }
    }
  }
  .actice{
    background-color: skyblue;
  }
</style>

